Chemokines constitute a family of small cytokines that are produced in inflammation and regulate leukocyte recruitment (Baggiolini, M. et al., Adv. Immnunol., 55: 97-179 (1994); Springer, T. A., Annu. Rev. Physiol., 57: 827-872 (1995); and Schall, T. J. and K. B. Bacon, Curr. Opin. Immunol., 6: 865-873 (1994)). Chemokines are capable of selectively inducing chemotaxis of the formed elements of the blood (other than red blood cells), including leukocytes such as neutrophils, monocytes, macrophages, eosinophils, basophils, mast cells, and lymphocytes, such as T cells and B cells. In addition to stimulating chemotaxis, other changes can be selectively induced by chemokines in responsive cells, including changes in cell shape, transient rises in the concentration of intracellular free calcium ions ([Ca2 +]i), granule exocytosis, integrin upregulation, formation of bioactive lipids (e.g., leukotrienes) and respiratory burst, associated with leukocyte activation. Thus, the chemokines are early triggers of the inflammatory response, causing inflammatory mediator release, chemotaxis and extravasation to sites of infection or inflammation.
The chemokines are related in primary structure and share four conserved cysteines, which form disulfide bonds. Based upon this conserved cysteine motif, the family can be divided into distinct branches, including the C-X-C chemokines (xcex1-chemokines) in which the first two conserved cysteines are separated by an intervening residue (e.g., IL-8, IP-10, Mig, I-TAC, PF4, ENA-78, GCP-2, GROxcex1, GROxcex2, GROxcex3, NAP-2, NAP-4), and the C-C chemokines (xcex2-chemokines), in which the first two conserved cysteines are adjacent residues (e.g., MIP-1xcex1, MIP-1xcex2, RANTES, MCP-1, MCP-2, MCP-3, I-309)(Baggiolini, M. and Dahinden, C. A., Immunology Today, 15:127-133 (1994)). Most CXC-chemokines attract neutrophil leukocytes. For example, the CXC-chemokines interleukin 8 (IL-8), GRO alpha (GROxcex1), and neutrophil-activating peptide 2 (NAP-2) are potent chemoattractants and activators of neutrophils. The CXC-chemokines designated Mig (monokine induced by gamma interferon) and IP-10 (interferon-gamma inducible 10 kDa protein) are particularly active in inducing chemotaxis of activated peripheral blood lymphocytes. CC-chemokines are generally less selective and can attract a variety of leukocyte cell types, including monocytes, eosinophils, basophils, T lymphocytes and natural killer cells. CC-chemokines such as human monocyte chemotactic proteins 1-3 (MCP-1, MCP-2 and MCP-3), RANTES (Regulated on Activation, Normal T Expressed and Secreted), and the macrophage inflammatory proteins 1xcex1and 1xcex2(MIP-1xcex1and MIP-1xcex2) have been characterized as chemoattractants and activators of monocytes or lymphocytes, but do not appear to be chemoattractants for neutrophils.
Chemokines (e.g., CC- and CXC-chemokines) act through receptors which belong to a superfamily of seven transmembrane spanning G protein-coupled receptors (Murphy, P. M., Annu. Rev. Immunol., 12: 593-633 (1994); Gerard, C. and N. P. Gerard, Curr. Opin. Immunol., 6: 140-145 (1994)). This family of G protein-coupled (serpentine) receptors comprises a large group of integral membrane proteins, containing seven transmembrane-spanning regions. The receptors are coupled to G proteins, which are heterotrimeric regulatory proteins capable of binding GTP and mediating signal transduction from coupled receptors, for example, by the production of intracellular mediators.
The chemokine receptors can be divided into groups, which include, CC-chemokine receptors 1 through 9 (CCR1-CCR9), which can bind certain CC-chemokines, and CXC-chemokine receptors 1 through 4 (CXCR1-CXCR4), which can bind certain CXC-chemokines. In general, the CC-chemokine receptors occur on several types of leukocytes, and are important for the migration of monocytes, eosinophils, basophils, and T cells (Qin, S. et al., Eur. J. Immunol., 26: 640-647 (1996); Carr, M.W. et al., Proc. Natl. Acad. Sci. USA, 91(9): 3652-3656 (1994); Taub, D. D. et al., J. Clin. Invest., 95(3): 1370-1376 (1995); Neote, K. et al., Cell, 72: 415-425 (1993); Gao, J.-L. et al., J. Exp. Med., 177: 1421-1427 (1993); Charo, I. F. et al., Proc. Natl. Acad. Sci. USA, 91: 2752-2756 (1994); Myers, S. J. et al., J. Biol. Chem., 270: 5786-5792 (1995); Combadiere, C. et al., J. Biol. Chem., 270(27): 16491-16494 (1995); Ponath, P. D. et al, J. Exp. Med., 183: 2437-2448 (1996); Daugherty, B. L. et al., J. Exp. Med., 183: 2349-2354 (1996); Power, C. A. et al., J. Biol. Chem., 270: 19495-19500 (1995); Hoogewerf, A. J. et al., Biochem. Biophys. Res. Commun., 218: 337-343 (1996); and Samson, M. et al., Biochemistry, 35: 3362-3367 (1996)).
In contrast, the two IL-8 receptors, CXCR1 and CXCR2, are largely restricted to neutrophils and are important for the migration of neutrophils (Baggiolini, M. et al., Adv. Immunol., 55: 97-179 (1994)). The L-8 receptors, CXCR1 (IL-8R1, interleukin-8 receptor type 1; Holmes, W. E. et al., Science, 253: 1278-1280 (1991)) and CXCR2 (IL-8R2, interleukin-8 receptor type 2; Murphy, P. M. and H. L. Tiffany, Science, 253: 1280-1283 (1991)) both bind IL-8 and appear to recognize the NH2-terminal Glu-Leu-Arg (ELR) motif as an essential binding epitope observed in CXC-chemokines that induce neutrophil chemotaxis (Clark-Lewis, I. et al., J. Biol. Chem., 266: 23128-23134 (1991); Hebert, C. A. et al., J. Biol. Chem., 266: 18989-18994 (1991); and Clark-Lewis, I. et al., Proc. Natl. Acad. Sci. USA, 90: 3574-3577 (1993)). The CXCR1 receptor of human neutrophils binds only IL-8 with high affinity, while the CXCR2 receptor binds IL-8 with similar affinity as CXCR1 but also binds other ELR-containing CXC-chemokines (Baggiolini, M. et al., Adv. Immunol., 55: 97-179 (1994)). Both receptors are capable of coupling to the same G protein xcex1-subunits, exhibiting functional. coupling to Gxcex1i2, Gxcex1i 3, Gxcex114, Gxcex115, and Gxcex116 (Wu, et al., Science, 261: 101-103 (1993)). Whether these two receptor subtypes play distinct physiologic roles is not clear.
In contrast to granulocytes and monocytes, lymphocyte responses to chemokines are not well understood. Notably, none of the receptors of known specificity appear to be restricted to lymphocytes and the chemokines that recognize these receptors cannot, therefore, account for events such as the selective recruitment of T lymphocytes that is observed in T cell-mediated inflammatory conditions. Moreover, although a number of proteins with significant sequence similarity and similar tissue and leukocyte subpopulation distribution to known chemokine receptors have been identified and cloned, the ligands for these receptors remain undefined. Thus, these proteins are referred to as orphan receptors. The characterization of the ligand(s) of a receptor, is essential to an understanding of the interaction of chemokines with their target cells, the events stimulated by this interaction, including chemotaxis and cellular activation of leukocytes, and the development of therapies based upon modulation of receptor function.
A chemokine receptor that binds the CXC-chemokines IP-10 and Mig has been cloned and characterized (Loetscher, M. et al., J. Exp. Med., 184: 963-969 (1996)). The receptor mediates Ca2 + (calcium ion) mobilization and chemotaxis in response to EP-10 and Mig. CXCR3 expressing cells show no significant response to the CXC-chemokines IL-8, GROxcex1, NAP-2, GCP-2 (granulocyte chemotactic protein-2), ENA78 (epithelial-derived neutrophil-activating peptide 78), PF4 (platelet factor 4), or the CC-chemokines MCP-1, MCP-2, MCP-3, MCP-4, MIP-1xcex1, MIP-1xcex2, RANTES, I309, eotaxin or lymphotactin. Moreover, a third ligand for CXCR3, I-TAC (Interferon-inducible T cell Alpha Chemoattractant), has also been found to bind to the receptor with high affinity and mediate functional responses (Cole, K.E. et al., J. Exp. Med., 187: 2009-2021 (1998)).
The restricted expression of human CXCR3 in activated T lymphocytes and the ligand selectivity of CXCR3 are noteworthy. The human receptor is highly expressed in IL-2 activated T lymphocytes, but was not detected in resting T lymphocytes, monocytes or granulocytes (Qin, S. et al., J. Clin. Invest., 101: 746-754 (1998)). Additional studies of receptor distribution indicate that it is mostly CD3+ cells that express CXCR3, including cells which are CD95+, CD45RO+, and CD45RAlow, a phenotype consistent with previous activation, although a proportion of CD20+ (B) cells and CD56+ (NK) cells also express this receptor. The selective expression in activated T lymphocytes is of interest, because other receptors for chemokines which have been reported to attract lymphocytes (e.g., MCP-1, MCP-2, MCP-3, MIP-1xcex1, MIP-1xcex2, RANTES) are also expressed by granulocytes, such as neutrophils, eosinophils, and basophils, as well as monocytes. These results suggest that the CXCR3 receptor is involved in the selective recruitment of effector T cells.
CXCR3 recognizes unusual CXC-chemokines, designated IP-10, Mig and I-TAC. Although these belong to the CXC-subfamily, in contrast to IL-8 and other CXC-chemokines which are potent chemoattractants for neutrophils, the primary targets of IP-10, Mig and I-TAC are lymphocytes, particularly effector cells such as activated or stimulated T lymphocytes and natural killer (NK) cells (Taub, D. D. et al., J. Exp. Med., 177: 18090-1814 (1993); Taub, D. D. et al., J. Immunol., 155: 3877-3888 (1995); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)). (NK cells are large granular lymphocytes, which lack a specific T cell receptor for antigen recognition, but possess cytolytic activity against cells such as tumor cells and virally infected cells.) Consistently, IP-10, Mig and I-TAC lack the ELR motif, an essential binding epitope in those CXC-chemokines that efficiently induce neutrophil chemotaxis (Clark-Lewis, I. et al., J. Biol. Chem. 266: 23128-23134 (1991); Hebert, C. A. et al., J. Biol. Chem., 266: 18989-18994 (1991); and Clark-Lewis, I. et al., Proc. Natl. Acad. Sci. USA, 90: 3574-3577 (1993)). In addition, both recombinant human Mig and recombinant human IP-10 have been reported to induce calcium flux in tumor infiltrating lymphocytes (TIL) (Liao, F. et al., J. Exp. Med., 182: 1301-1314 (1995)). While IP-10 has been reported to induce chemotaxis of monocytes in vitro (Taub, D. D. et al., J. Exp. Med., 177: 1809-1814 (1993), the receptor responsible has not been identified), human Mig and I-TAC appear highly selective, and do not show such an effect (Liao, F. et al., J. Exp. Med., 182: 1301-1314 (1995); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021(1998)). IP-10 expression is induced in a variety of tissues in inflammatory conditions such as psoriasis, fixed drug eruptions, cutaneous delayed-type hypersensitivity responses, tuberculoid leprosy, and in experimental glomerulonephritis, and experimental allergic encephalomyelitis. IP-10 has a potent in vivo antitumor effect that is T cell dependent, is reported to be an inhibitor of angiogenesis in vivo and can induce chemotaxis and degranulation of NK cells in vitro, suggesting a role as a mediator of NK cell recruitment and degranulation (in tumor cell destruction, for example) (Luster, A. D. and P. Leder, J. Exp. Med., 178: 1057-1065 (1993); Luster, A. D. et al., J. Exp. Med. 182: 219-231 (1995); Angiolillo, A. L. et al., J. Exp. Med., 182: 155-162 (1995); Taub, D. D. et al., J. Immunol., 155: 3877-3888 (1995)). The expression patterns of IP-10, Mig and I-TAC are also distinct from that of other CXC chemokines in that expression of each is induced by interferon-gamma (IFNxcex3), while the expression of IL-8 is down-regulated by IFNxcex3 (Luster, A. D. et al., Nature, 315: 672-676 (1985); Farber, J. M., Proc. Natl. Acad. Sci. USA, 87: 5238-5242 (1990); Farber, J. M., Biochem. Biophys. Res. Commun., 192 (1): 223-230 (1993), Liao, F. et al., J. Exp. Med., 182: 1301-1314 (1995); Seitz, M. et al., J. Clin. Invest., 87: 463-469 (1991); Galy, A. H. M. and H. Spits, J. Immunol., 147: 3823-3830 (1991); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)).
Chemokines are recognized as the long-sought mediators for the recruitment of lymphocytes. Several CC-chemokines were found to elicit lymphocyte chemotaxis (Loetscher, P. et al., FASEB J, 8: 1055-1060 (1994)), however, they are also active on granulocytes and monocytes (Uguccioni, M. et al., Eur. J. Immunol., 25: 64-68 (1995); Baggiolini, M. and C. A. Dahinden, Immunol. Today, 15: 127-133 (1994)). The situation is different for IP-10, Mig and I-TAC, which are selective in their action on lymphocytes, including activated T lymphocytes and NK cells, and which bind CXCR3, a receptor which does not recognize numerous other chemokines and which displays a selective pattern of expression.
In view of these observations, it is reasonable to conclude that the formation of the characteristic infiltrates in inflammatory lesions, such as, for example, delayed-type hypersensitivity lesions, sites of viral infection and certain tumors is a process mediated via CXCR3 and regulated by CXCR3 expression. Lymphocytes, particularly T lymphocytes, bearing a CXCR3 receptor as a result of activation can be recruited into inflammatory lesions, sites of infection and/or tumors by IP-10, Mig and/or I-TAC, which can be induced locally by interferon-gamma. Thus, CXCR3 plays a role in the selective recruitment of lymphocytes, particularly effector cells such as activated or stimulated T lymphocytes.
Many existing drugs have been developed as antagonists of the receptors for biogenic amines, for example, as antagonists of the dopamine and histamine receptors. However, no antagonists of the receptors for larger proteins such as chemokines and C5a have been successfully developed and marketed. Small molecule antagonists of the interaction between CXC-chemokine receptors and their ligands, including IP-10, Mig and I-TAC, would provide compounds useful for inhibiting harmful inflammatory processes xe2x80x9ctriggeredxe2x80x9d by receptor ligand interaction, as well as valuable tools for the investigation of receptor-ligand interactions.
Diaminoethylene derivatives possessing an electron withdrawing group(s) are known as histamine H2 receptor antagonists and as drugs useful for treating peptic ulcers (Principles of Medicinal Chemistry, Foye, W. O., Ed. Lea and Febiger, Philadelphia, 1989, 3rd ed.).
The present invention relates to small organic compounds which modulate chemokine receptor activity and are useful in the treatment (e.g., palliative therapy, curative therapy, prophylactic therapy) of certain diseases and conditions e.g., inflammatory diseases (e.g., psoriasis), autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis), graft rejection (e.g., allograft rejection, xenograft rejection), infectious diseases, cancers. It has now been found that a number of small organic molecules are antagonists of chemokine receptor function (e.g., CXCR3), and can inhibit leukocyte activation and/or recruitment. An antagonist of chemokine receptor function is a molecule which can inhibit the binding of one or more chemokines to one or more chemokine receptors on leukocytes and/or other cell types. As a consequence, and by virtue of the fact that antagonists lack chemokine agonist properties, processes and cellular responses mediated by chemokine receptors can be inhibited with these small organic molecules. In one aspect, the invention relates to small organic compounds which are antagonists of CXCR3. Such CXCR3 antagonists can inhibit binding of one or more chemokines (e.g., CXC-chemokines, such as IP-10, Mig and/or I-TAC) to CXCR3.
The invention also relates to a method of modulating (inhibiting or promoting) an inflammatory response in an individual in need of such therapy. The method comprises administering a therapeutically effective amount of a compound (e.g., small organic molecule) which inhibits or promotes mammalian CXCR3 function to an individual in need thereof.
The invention also relates to a method of treating an individual having a disease associated with pathogenic leukocyte recruitment and/or activation, such as the inflammatory and autoimmune diseases discussed herein. The method comprises administering to the individual a therapeutically effective amount of a compound or small organic molecule which is an antagonist of chemokine receptor function. Compounds or small organic molecules which have been identified as antagonists of chemokine receptor function are discussed in detail herein, and can be used for the manufacture of a medicament for treating or preventing a disease associated with pathogenic leukocyte recruitment and/or activation.
The invention further relates to a compound or small organic molecule described herein for use in therapy (including prophylaxis) or diagnosis, and to the use of such a compound or small organic molecule for the manufacture of a medicament for the treatment of a particular disease or condition as described herein (e.g., inflammatory disease, cancer, autoimmune disease, graft rejection, allergic disease).
The invention also includes pharmaceutical compositions comprising one or more of the compounds or small organic molecules which have been identified herein as antagonists of chemokine function and a suitable pharmaceutical carrier. The invention further relates to novel compounds which can be used to treat an individual with a disease associated with inflammation and/or pathogenic leukocyte recruitment and/or activation.